184 
ON MEDICINAL EXTRACTS. 
Extracted from the Transactions of the Society of Arts, 
Vol. XLV. p. 71. 
IT is well known to professional men, that the juices of almost 
all plants are more or less injured in their medicinal qualities 
by- being boiled down, and evaporated in the usual way to the 
consistence of extract. 
^ At Apothecaries’ Hall the evaporation is entirely eflfected by 
means of steam, so that the heat employed is under complete 
control; and in Mr. Barry’s patent process the evaporation is 
performed in vacuo. 
The process of Mr. Houlston (to whom the thanks of the 
society were voted) is the following :—The plant being bruised 
is to be submitted to the action of a press in order to squeeze 
out the juice, which is then to be pressed through fine linen. 
The depurated juice is now to be poured to the depth of about 
one-eighth of an inch into an earthenware plate, or a glass dish, 
and is to be placed in a constant current of air, by placing it on 
the inner side of a window, and raising the sash about an inch’. 
The constant current of air thus produced occasions the rapid 
evaporation of the watery parts, and there remains a soft extract, 
retaining the colour, odour, and medical properties of the recent 
plant, with less alteration than by any other method. If the 
sun shines a blind should be hung before the window, as vege¬ 
table juices are speedily changed by the action of solar light. 
The consistence given to the extract is entirely optional; but 
those that are rather hard will keep better than those that 
are soft. 
This method is not adapted to a manufactory on a large scale ; 
but any individual practitioner may, without much trouble or 
expense, prepare in this way, for his own use, extracts far su¬ 
perior, in active properties, to those that are usually met with. 
Cases or Communications, addressed to the Editor of the Veterinariany at the 
Printer's, (post paid) will meet with due consideration. 
4 
John Hill, Printei’, Black Horse Court, Fleet Street, 
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